Heretofore, there has been known an exhaust aftertreatment device comprising a first treatment section capable of removing a first component contained in exhaust gas of an engine and a second treatment section capable of removing a second component contained in the exhaust gas.
For example, an exhaust aftertreatment device described in JP 2009-79422A (hereinafter referred to as “Patent Literature 1”) comprises: a first treatment section having a filter (Diesel Particulate Filter) for trapping particulate matter (hereinafter referred to as “PM”) as one example of the first component; and a second treatment section having a catalyst for promoting a selective catalytic reduction (hereinafter referred to as “SCR”) reaction of nitrogen oxides (hereinafter referred to as “NOx”) as one example of the second component.
A construction machine described in the Patent Literature 1 further comprises a frame, and an engine provided on the frame. The first treatment section and the second treatment section are arranged side-by-side laterally (in a right-left direction) on the frame.
Meanwhile, in recent years, there has been growing demand for expanding the range of application of an exhaust aftertreatment device to smaller construction machines. In this regard, a small-sized construction machine has serious restriction in terms of space on the frame, so that it is difficult to ensure, on the frame, a space for arranging the first treatment section and the second treatment section in laterally side-by-side relation as in the exhaust aftertreatment device described in Patent Literature 1.
As measures to cope with this situation, it is conceivable to arrange the first treatment section and the second treatment section in one-above-the-other and side-by-side relation (side-by-side in an up-down direction). In this case, however, a gravity center of the exhaust aftertreatment device is shifted to a higher position, as compared to the case where the first treatment section and the second treatment section are arranged in laterally side-by-side relation. This causes difficulty in stably supporting the exhaust aftertreatment device on the frame.